Polymer blends of ethylene-propylene (EP) polymers or of ethylene-propylene-diene (EPDM) polymers with .alpha.-monoolefin polymers, particularly with polyethylenes, are known in the art (see U.S. Patent Nos. 3,176,052; 3,328,486; 3,361,850 and 3,751,521). At times, curing or crosslinking agents are added to effect chemical changes in the nature of the blends (see U.S. Patent Nos. 3,564,080 and 3,806,558). Polymer blends described in U.S. Patent Nos. 3,785,643 and 3,806,558 are stated to be thermoplastic in nature. They are prepared by partially crosslinking the polymers, particularly the EPDM polymers.
U.S. Patents 3,784,668 and 3,808,047 teach blends of polyethylene with copolymers of ethylene and a polar monomer or ester comonomer. U.S. Patent 3,821,333 discloses a T gasket for lens molds, made from a mixture of ethylene co- or terpolymers (and possibly polyethylene), such as ethylene-vinyl acetate, ethylene-ethyl acrylate, ethylene-propylene, and ethylene-propylene-diene copolymers. Finally, U.S. Patent 3,919,358 teaches blends having superior tensile strength comprising an EPDM polymer having a high degree of unstretched crystallinity, together with a polyethylene.
The polymer blends of the present invention are thermoplastic in nature, and do not require curing or crosslinking agents in their preparation. Additionally, the tensile strengths of the blends of the present invention are superior to that predicted from the individual contributive effects of the polymer components, i.e., greater than any one polymer component of the blends. Blend tensile strengths may be improved further by including therein at least one polyethylene.